Marc-Alexander Brockmann

Active push deployment technique improves stent/vessel-wall interaction in endovascular treatment of acute stroke with stent retrievers.

Background The optimal interaction between stent struts and thrombus is crucial for successful revascularization in endovascular stroke therapy with stent retrievers. Deploying the stent retriever by actively pushing it into the thrombus increases the radial force with which the stent struts expand into the thrombus. Objective To examine the active push deployment (APD) technique in an in vitro model and present our clinical experience with this technique. Methods In an in vitro experiment we investigated the configuration of a Solitaire and a Trevo ProVue device (both 4×20 mm), depending on whether the devices were deployed using the APD technique or simple unsheathing. We retrospectively assessed the effectiveness and safety of this technique by analyzing 130 patients with large vessel occlusions (carotid T or M1 segment of the middle cerebral artery), who received endovascular treatment with a Trevo device (4×20 mm) that was deployed using the APD technique. Results In vitro experiment: the APD technique improved apposition of the devices to the vessel wall. There was widening of 30% (Trevo) and 19% (Solitaire) at the cost of a shortening of 5% and 4%, respectively, when the devices were deployed in a carotid T model. Clinical study: the revascularization rate (Thrombolysis in Cerebral Infarction ≥2b) with the Trevo device was 90%. There were no retriever-associated dissections or perforations in 278 retrieval maneuvers. Conclusions The APD technique improves apposition of the tested devices to the vessel wall. The widening effect comes at the cost of minimal shortening of the devices. Our clinical experience shows that using the APD technique to deploy the Trevo device is effective and safe.

Optimizing endovascular stroke treatment: removing the microcatheter before clot retrieval with stent-retrievers increases aspiration flow.

Background Flow control during endovascular stroke treatment with stent-retrievers is crucial for successful revascularization. The standard technique recommended by stent-retriever manufacturers implies obstruction of the respective access catheter by the microcatheter, through which the stent-retriever is delivered. This, in turn, results in reduced aspiration during thrombectomy. In order to maximize aspiration, we fully retract the microcatheter out of the access catheter before thrombectomy—an approach we term the ‘bare wire thrombectomy’ (BWT) technique. We verified the improved throughput with systematic in vitro studies and assessed the clinical effectiveness and safety of this method. Methods We compared aspiration flow of water through various access catheters (5–8 F) with a Rebar microcatheter (0.18 inch and 0.27 inch) and a Trevo stent-retriever using the standard technique and the BWT technique in vitro. We also retrospectively analyzed 302 retrieval maneuvers in 117 patients who received endovascular treatment with a stent-retriever between February 2010 and April 2015. Results In the in vitro experiment, removal of the microcatheter in all tested settings resulted in significantly increased aspiration flow through the access catheter (p<0.001). This effect was particularly pronounced in access catheters with a diameter of ≤7 F. In the clinical study, the revascularization rate (Thrombolysis In Cerebral Infarction ≥2b) was 91%. There were no complications associated with the BWT technique in 302 retrieval maneuvers. Conclusions The BWT technique results in improved aspiration flow rates compared with the standard deployment technique. Our clinical data show that the BWT technique is effective and safe.

Retrieval of Migrated Coils with Stent Retrievers: An Animal Study

BACKGROUND AND PURPOSE: Coil migration is a potentially serious complication of endovascular aneurysm treatment. The aim of the study was to systematically investigate the effectiveness of coil retrieval with a stent retriever in an animal model. MATERIALS AND METHODS: A total of 148 coils of various types and sizes were placed into arteries of varying diameters in a porcine in vivo model. Coil retrieval was performed by placing a Trevo ProVue stent retriever over the coil and trying to trap a part of the platinum coil within the stent mesh by advancing the microcatheter over the stent or simply by retrieving the stent without trying to trap the coil by advancing the microcatheter. RESULTS: Coil retrieval was successful in 101 of 102 cases (99%), in which trapping of the coil within the stent retriever by advancing the microcathter was applied. When we only pulled back the stent without trapping the coil, retrieval was successful in only 5 of 46 cases (11%). Coil type, coil structure (2D versus 3D), actual coil shape in the affected vessel, investigator experience, aspiration, coil localization, and vessel diameter had no significant influence on retrieval outcome. There was no case of vessel perforation. CONCLUSIONS: Retrieval of migrated platinum coils with a stent retriever is an effective treatment option for migrated coils when the correct technique is applied.

Abciximab does not prevent ischemic lesions related to cerebral angiography: a randomized placebo-controlled trial.

Background: To assess the efficiency of IIb/IIIa platelet receptor inhibition by abciximab in the prevention of silent embolism during digital subtraction angiography. Methods: In this randomized, double-blind, prospective study, pre- and postangiographic diffusion-weighted magnetic resonance imaging (DWI) of 184 participants was evaluated for the occurrence of silent embolism. Results: No significant relationship was found between the patients receiving abciximab before digital subtraction angiography (15 of 90; 16.7%) and patients in the placebo group (16 of 94; 17.0%) regarding postangiographic appearance of silent emboli (p = 0.9). Conclusions: IIb/IIIa receptor inhibition by abciximab does not diminish the occurrence of silent embolism during digital subtraction angiography. Our findings indicate that solid blood clots are not the origin of hyperintense lesions observed on DWI and enhance the role of alternative mechanisms.

Molecular Ultrasound Imaging of αvβ3-Integrin Expression in Carotid Arteries of Pigs After Vessel Injury.

ObjectivesInterventions such as balloon angioplasty can cause vascular injury leading to platelet activation, thrombus formation, and inflammatory response. This induces vascular smooth muscle cell activation and subsequent re-endothelialization with expression of &agr;v&bgr;3-integrin by endothelial cells and vascular smooth muscle cell. Thus, poly-N-butylcyanoacrylate microbubbles (MBs) targeted to &agr;v&bgr;3-integrin were evaluated for monitoring vascular healing after vessel injury in pigs using molecular ultrasound imaging. Materials and MethodsApproval for animal experiments was obtained. The binding specificity of &agr;v&bgr;3-integrin–targeted MB to human umbilical vein endothelial cells was tested with fluorescence microscopy. In vivo imaging was performed using a clinical ultrasound system and an 8-MHz probe. Six mini pigs were examined after vessel injury in the left carotid artery. The right carotid served as control. Uncoated MB, cDRG-coated MB, and &agr;v&bgr;3-integrin–specific cRGD-coated MB were injected sequentially. Bound MBs were assessed 8 minutes after injection using ultrasound replenishment analysis. Measurements were performed 2 hours, 1 and 5 weeks, and 3 and 6 months after injury. In vivo data were validated by immunohistochemistry. ResultsSignificantly stronger binding of cRGD-MB than MB and cDRG-MB to human umbilical vein endothelial cells was found (P < 0.01). As vessel injury leads to upregulation of &agr;v&bgr;3-integrin, cRGD-MBs bound significantly stronger (P < 0.05) in injured carotid arteries than at the counter side 1 week after vessel injury and significant differences could also be observed after 5 weeks. After 3 months, &agr;v&bgr;3-integrin expression decreased to baseline and binding of cRGD-MB was comparable in both vessels. Values remained at baseline also after 6 months. ConclusionsUltrasound imaging with RGD-MB is promising for monitoring vascular healing after vessel injury. This may open new perspectives to assess vascular damage after radiological interventions.

Feasibility of combined surgical and endovascular carotid access for interventional treatment of ischemic stroke

Background Rapid recanalization of occluded vessels is crucial for good clinical outcome in acute ischemic stroke. Endovascular treatment is usually performed via a transfemoral approach, but catheterization of the carotid arteries can be problematic in cases of difficult anatomy or vascular pathologies in some cases. Objective To describe our experience with a technique involving surgical access to the carotid artery and consecutive transcarotid endovascular thrombectomy in patients with acute stroke. Methods In a retrospective review of a prospectively maintained registry we identified 6 patients who underwent acute endovascular thrombectomy via a surgical access to the carotid artery. Results Admission National Institute of Health Stroke Scale (NIHSS) ranged from 7 to 23. Intracranial recanalization (thrombolysis in cerebral infarction, TICI≥2b) was achieved in all patients (100%). Recanalization was achieved within 19±5 min after establishing carotid access. One patient developed a small neck hematoma, which was surgically removed without complications. No complications related to endovascular therapy were seen. At 3 months’ follow-up, five patients had survived. Three patients (50%) had regained excellent neurological function (modified Rankin Scale, mRS 0–1). Conclusions Surgical carotid access for endovascular stroke treatment is feasible, with considerable advantages, in patients with expected problematic access or for whom transfemoral endovascular carotid access has failed.

Weekend effect in endovascular stroke treatment: do treatment decisions, procedural times, and outcome depend on time of admission?

Background Epidemiologic studies identified a ‘weekend effect’ or ‘out-of-hours effect’, which implies that procedural and clinical outcomes of patients with stroke, who are admitted out-of-hours, are less favorable than for patients admitted during working-hours. Objective To determine (1) whether our procedural times and clinical outcome were affected by an out-of-hours effect and (2) whether the decision in favor of, or against, endovascular stroke treatment (EST) depends on the time of admission. Methods Between February 2010 and January 2015, 6412 consecutive patients presenting with symptoms of acute ischemic stroke were evaluated for EST eligibility according to established local protocols and generally accepted consensus criteria, and dichotomized into working-hours and out-of-hours cohorts according to admission times. Within both groups, patients given EST were identified and the rate of treatment decision, procedural times, and clinical outcome were compared and analyzed. Results Clinical and radiological features of patients admitted in working-hours and out-of-hours did not differ significantly. Procedural times and clinical outcome were not affected by an out-of-hours effect (p≥0.054). 221/240 (92.1%) out-of-hours patients and 154/166 (92.8%) working-hours patients who were eligible for EST were transferred to the angiography suite for EST (p=0.798). The rationale not to treat patients who were eligible for EST did not differ between working-hours and out-of-hours admission (p=0.756). Conclusions It is possible to produce competitive procedural times regardless of the time of admission and to prevent a treatment decision bias when standard operating procedures are applied consistently.

Development of a Polymer-Based Biodegradable Neurovascular Stent Prototype: A Preliminary In Vitro and In Vivo Study

Biodegradable stents are not established in neurovascular interventions. In this study, mechanical, radiological, and histological characteristics of a stent prototype developed for neurovascular use are presented. The elasticity and brittleness of PLA 96/4, PLDL 70/30, PCL, and PLGA 85/15 and 10/90 polymers in in vitro experiments are first analyzed. After excluding the inapt polymers, degradability and mechanical characteristics of 78 PLGA 85/15 and PLGA 10/90 stent prototypes are analyzed. After excluding PLGA 10/90 stents because of rapid loss of mass PLGA 85/15 stents in porcine in vivo experiments are analyzed. Angiographic occlusion rates 7 d, 1 month, 3 months, and 6 months after stent implantation are assessed. Histological outcome measures are the presence of signs of inflammation, endothelialization, and the homogeneity of degradation after six months. One case of stent occlusion occurs within the first 7 d. There is a prominent foreign-body reaction with considerable mononuclear and minor granulocytic inflammation combined with incomplete fragmental degradation of the struts. It is possible to produce a stent prototype with dimensions that fit the typical size of carotid arteries. Major improvements concerning thrombogenicity, degradation, and inflammatory response are required to produce biodegradable stents that are suitable for neurovascular interventions.